Objectives of his study are: (1) To identify patient characteristics which predict adherence or nonadherence to antihypertension regimens; (2) To determine the costs and effectiveness of three interventions in improving adherence; and (3) To determine patient characteristics which predict the success of each intervention. The study consists of two phases: (1) A retrospective analysis of adherence behavior in a cohort of hypertension patients currently under treatment; and (2) A prospective intervention trial directed at improving adherence behavior in a "new" but similar population of hypertensive patients.